Various devices have heretofore been proposed for catching crabs. For example Koenig U.S. Pat. No. 1,403,171 discloses a crab trap having a net attached to a frame something like that of an umbrella. The frame comprises a central stem to the end of which six ribs are pivotally attached. Stretchers are connected at one end to the respective ribs and at the other end to a runner which is slidable on the stem. When the device is lowered to the bottom it opens up by gravity so that the net is spread on the bottom. When the trap is raised by a line attached to the runner, the ribs are folded up so that the net forms a pocket.
Glasser Pat. No. 2,652,656 discloses a trap having four flexible ribs emanating from a cross-shaped spider provided on the upper portion of a central shaft. A set of rods are pivotally connected at one end to brackets secured to intermediate portions of the ribs and at the other end to a further spider which is slidable on the central shaft but has a spring detent for holding it in set position. A square net is attached at its corners to the lower ends of the ribs. The trap is closed by a sharp jerk upwardly on a line attached to the central shaft.
Mears U.S. Pat. No. 2,728,164 discloses a crab trap comprising a plurality of legs which slope inwardly from a ring to which a sheet of wire mesh is secured. A collapsible net secured to the ring is adapted to be moved between a position lying on the surface upon which the trap is placed to a position lying against the legs to form a pocket which is, however, open at the top.